Hello. I have a 97 960 Wagon with low miles. I think, however, that the rotors might be warped or grooved and I would like to replace them. I took a wheel off and noticed, unlike my previous vehicle, that there's a small brass nipple thingy sticking out of the rotor. I cannot just tap the rotor from the back to get it off and slide a new one on....evidently. What is this brass thing...some sort of temperature sensor? How do I replace the rotors? Do I unscrew this thing? Any insight, along with instructions for this proceedure, would be much appreciated.

David Moran, Arlington, Va.